Previously stationed in the Persian Gulf during the Iran-Iraq war, the USS Vincennes was in the Straight of Hormuz, a body of water that the aircraft would have to pass over on its route. The USS Vincennes was sailing in Iranian waters, along with the USS Sides and USS Elmer Montgomery, and had just been in the midst of combat with Iranian vessels.

The inexperienced crewmembers believed the aircraft’s flight pattern and speed matched that of an Iranian fighter descending at high speed toward the ship. The Navy said it attempted to contact Iran Flight 655 numerous times on civilian radio frequencies, never receiving a response. The Vincennes fired, killing all 290 people on board the plane.

Citing recent attacks, the U.S. government made it clear that there was an eminent threat of attack on the U.S. Navy. According to the Navy, only after other alternatives were exhausted did the Vincennes crew justifiably act in self-defense to what it perceived to be a threat during a time of war.

According to a letter written to Congress by President Ronald Reagan on July 4, the Vincennes was “firing in self-defense at what it believed to be a hostile Iranian military aircraft.”

The attack on Flight 655 occurred during the eight-year war between Iran and Iraq. The war broke out over both nations' claims to the oil-rich area along their shared border. The exact number of casualties is unclear but it is estimated that 1 to 2 million people died as a result of the conflict, according to Encyclopedia Britannica.

Approximately a year prior to the Vincennes incident, in 1987, a rogue Iraqi Mirage F-1 fighter launched two Exocet missiles at the USS Stark, killing more than 30 sailors. The attack was unprovoked and the Stark, not expecting it, did not take defensive measures. The Stark was struck by the first of two missiles as it attempted to contact the Iraqi fighter via radio to issue a warning.

Some observers said memories of the slow American response to an Iraqi air attack on the USS Stark a year earlier, as well as the wartime environment of the Iran-Iraq war, may have induced panic in the crew. But Iran believed that the attack was deliberate, and many journalists suspected a U.S cover-up, speculating that the Navy, anxious for wartime action, had been overly aggressive, reported Newsweek.